synchrotron radiation

A gas target is like a funnel: the steeper its walls, the stronger the flow. But in this funnel, it is not water that flows, but ultraviolet light, born when a powerful laser pulse passes through a cloud of argon. The efficiency of this conversion is usually minuscule, about 0.001%: out of a thousand laser photons, only one turns into useful ultraviolet.

Light born when a fast electron enters a material is usually assumed to be the same in all directions. But in crystals where optical properties depend on direction, that's not the case. Run your hand over velvet: one way it's smooth and shiny, the other — dark and rough. Similarly, a crystal responds differently to light depending on how it's oriented.

In a dark room, a spark jumps between two wires, and for an instant, there is light. Physicists have done something similar, but a million times smaller: at the boundary of two transparent crystals, they drew a conducting path and left a break just a few atoms wide. When a direct voltage was applied across this tiny gap, it began to glow.

A laser hits an atom, and tears out an electron. The brighter the light, the stronger the kick, and the faster the electron flies away. That's how the familiar picture works, where light is a smooth wave. But what if the light isn't smooth but 'squeezed,' with quantum fluctuations, like the trembling of a string?

A shooter aims at a target, pulls the trigger, and hears two shots: one loud, one quiet. That's how the new setup works, except instead of bullets, there's an electron bunch, and instead of shots, there are two flashes of light. One flash is X-ray, the other is terahertz. They fly to the same point with perfect timing.

A regular laser beam travels straight, like the light from a flashlight. But light can be twisted into a spiral, like the thread of a corkscrew. Such a beam carries orbital angular momentum: it doesn't just illuminate, it also spins anything it encounters.

A shooter aims at a target, pulls the trigger, and hears two shots: one loud, one quiet. That's how the new setup works, except instead of bullets, there's an electron bunch, and instead of shots, there are two flashes of light. One flash is X-ray, the other is terahertz. They fly to the same point with perfect timing.

In 1994–1995, the LEP accelerator collided electrons and positrons, producing Z bosons that promptly decayed into showers of particles. The DELPHI detector recorded these events, and now, decades later, a new pattern has been found in that data: the electric charge within particle jets is not distributed randomly but follows a simple sine curve.

A synchrotron beam is like a jet of water from a hose: wide and awkward for fine work. To examine a tiny sample, you need a fine needle, not a hose. In the new setup, the needle is a glass capillary — a tube through which light glides, reflecting off the walls like a voice echoing down a long corridor.

In July 1969, as Apollo 11 flew toward the Moon, astronauts noticed something unusual: brief flashes of light that appeared even with their eyes closed. At first, this was attributed to fatigue, but the flashes recurred in different crews. Gradually, it became clear: cosmic rays were to blame — tiny particles hurtling through space at tremendous speeds.

Two electrons that leave a metal needle tip almost simultaneously start to repel each other, like two people trying to squeeze through a narrow door at the same time. The closer they are, the more they get in each other's way.

A vortex in a magnetic material is like a whirlpool, but instead of water, the directions of magnetization twist. An electron flying through such a vortex feels not just a magnetic field, but a curvature of space: its path bends as if it were rolling down a funnel with a narrow neck.

The solar corona is the Sun's outer atmosphere, heated to millions of degrees. How it gets so hot is still unclear. One candidate is torsional waves: they twist magnetic field lines like a rubber band. Such waves were recently spotted with the new Daniel K. Inouye Solar Telescope.

A lighthouse that blinks not every second but once every few minutes or even hours. That is exactly how long-period radio transients behave — cosmic sources discovered only recently.

A laser beam is like a swift vortex that briefly captures a passing electron. As the particle moves through the pulse, its spin (the intrinsic rotation, like a tiny top) experiences a weak kick. After leaving the beam, the top no longer points in the same direction; it has turned a little.

An electron is not just a point. It is a probability cloud, smeared out in space. When such a cloud collides with a powerful laser pulse, it can emit a high-energy photon — a gamma quantum. And this photon can be not just ordinary but twisted, like a corkscrew, carrying orbital angular momentum.

A guitar string plucked exactly at its middle produces only odd overtones. The same prohibition holds in symmetric crystals: when light knocks out electrons, their re-emitted radiation contains only odd harmonics. But physicists have found a way to bypass this rule — without shifting a single atom. The secret is electric current.

A stone falls into still water, and smooth rings spread across the surface. If the stone doesn't just fall but also spins, tiny whirlpools, vortices, appear on the surface. Light can do the same, only instead of water, it's space and time themselves.

Radio astronomy began with the mysterious noise caught by the antenna of Karl Jansky and the rhythmic pulses that Jocelyn Bell Burnell playfully called 'little green men'.

In 1956, two radio telescopes at Jodrell Bank stared at Sirius, capturing not an image but the trembling of intensity.

The mystery of antimatter in space has long puzzled astrophysicists: where do positrons come from, settling like snowflakes into our detectors? The answer might lurk in the most ubiquitous gamma-ray background. The Universe is soaked in diffuse light — the cosmic photon background (CPB).

A thin film of a special crystal (for instance, molybdenum disulfide) sits on a microscope stage. The temperature is just above the point where the material becomes a superconductor.

A surfer glides across the ocean surface until a big wave comes, and then they're flying forward. Similarly, a free electron interacts with light: usually the energy exchange is barely noticeable, but if the surrounding medium begins to oscillate rhythmically, each wave crest pushes the particle harder and harder.

Even Jocelyn Bell Burnell, who first detected the strict periodicity of radio signals, noticed that some pulses would suddenly vanish. Today we know: variability is not a whim, but the voice of intricate electrodynamics.

When an electric charge moves with acceleration, it emits electromagnetic radiation, i.e., light — a familiar phenomenon in physics. However, researchers have found that when moving along a specially chosen trajectory, the radiation acquires unusual properties.

An ordinary diode in electronics works like a one-way street: current flows in only one direction. In superconductors, where electricity flows without resistance, such behavior has long been elusive — current is usually symmetric. The authors of the new work found a way to create a perfect superconducting diode using light.

Light loves symmetry: in an open channel, it flows equally both ways. To steer it one way, physicists often use magnets. A new approach does without, using rotation — just the speed of a vinyl record — and interference from two atoms. Rotation changes the “pitch” of light for different directions, just as a siren’s tone shifts when a car approaches or recedes.

Many black holes are surrounded by magnetic fields. As it spins, the black hole drags curved spacetime along with it, like a machine's flywheel, and sets the cosmic factory in motion.

In a boron nitride crystal, the perfect atomic lattice is sometimes disrupted: an atom is missing here, or replaced by a foreign one there. Under a powerful microscope, these tiny imperfections appear as traps for electrons: they capture particles and start to emit light, and they also respond to magnetic fields.

A flashlight beam aimed through frosted glass turns into a blurry spot with every extra millimeter of thickness. Scintillators, materials that convert X-rays into visible light, behave much the same way. They underpin medical imaging, baggage screening, and detectors at particle accelerators.

A pebble tossed into a pond sends ripples spreading in all directions. Now imagine the pond itself suddenly turning into jelly — instantly, faster than the wave can complete a single crest. Some ripples would keep spreading but change their spacing, while others would unexpectedly turn around and run back toward the point of impact, as if time were flowing backward for them.

A long, narrow garden bed needs watering, but you can't move the hose: you can only turn the water on and off. If you just open the tap, water flows in a steady stream and floods everything at once. But if you quickly flip the lever, you can send short bursts of water: each landing exactly where it's needed.

Sunlight hits a silicon wafer, and a current flows in the circuit. That's the familiar work of a solar cell: light knocks out electrons, and a p–n junction (the boundary between two layers with different conductivities) forces them to move in one direction. But in some crystals, current arises differently — without any junctions, purely from the material's internal structure.

When many excited atoms are gathered together, they often fire light in concert, like a crowd clapping in rhythm. This well-known phenomenon is called Dicke superradiance. But the authors of the new study asked: what happens if the atoms are not identical and each one feels its neighbors?

Light from a distant star is not just a steady stream. It oscillates like a wave and can vibrate in different directions. Usually these oscillations are indistinguishable, but a magnetar can sort them out.

When light swings past a massive body like a black hole, its path warps — an effect predicted by Einstein. New research has taken into account that near such objects, clouds of hadrons often swirl — the very particles we know from protons and neutrons in atomic nuclei.

A light carousel spins not people but electrons. Instead of wooden horses, there are invisible blades of light. This is exactly the kind of 'carousel' physicists built to give electrons a spin. Usually, to twist an electron beam into a vortex, you need a tiny mask — a stencil with slits carved on the atomic scale. Fabricating it is extremely challenging.

The solar wind, a stream of charged particles from the Sun, slams into the tenuous gas that fills the space between the stars. The collision produces a faint X-ray glow. For astronomers, this is like fog in front of headlights: it obscures distant objects.

A lantern shines through thick fog. Light scatters off water droplets, and the lantern appears blurred. Something similar happens around a black hole: hot gas, like fog, envelops it, while X-rays from the inner parts of the disk struggle through this cloud. Only here, the "droplets" are electrons, and the "fog" itself is called the corona.

Deep in space, a rapidly spinning neutron star, a pulsar nicknamed the Lighthouse, speeds through tenuous gas. Like a motorboat cutting through water, it leaves a glowing trail of charged particles behind. In X-rays, this trail appears as a bright tail and a thin filament stretching over many light-years.